Severe spark knock under partial throttle - Page 2
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, Severe spark knock under partial throttle in Past Cadillac Vehicle Discussion; Originally Posted by outsider if it's carbon build up then you should be able to clean it out with some ...
  1. #16
    jamespowers is offline Cadillac Owners Connoisseur
    Automobile(s): 1986 Brougham, 1975 Eldorado, 2008 Escalade
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    Re: Severe spark knock under partial throttle

    Quote Originally Posted by outsider View Post
    if it's carbon build up then you should be able to clean it out with some seafoam poured directly down the carb throat while running. Use about 1/2 bottle and start slow, gradually increasing your rate of pour until it chokes out the car and it shuts off. Let it sit for a few minutes and then start it back up. YOu'll see a lot of black crap come out of the tail pipe if it's carbon build up.
    I thought you put the Seafoam down the PCV hole or have the vacuum from the brake booster suck it into the engine. I have only put it in my gas tank so I am not sure here but I understood that running it through the PCV orifice would clean out the build up the best since that is where you see a heck of a lot of build up directly. Then again, I just had my carb rebuilt and don't want to put it down there and screw anything up I just got fixed.

  2. #17
    brougham is offline Cadillac Owners Master
    Automobile(s): 1991 Cadillac Brougham D'Elegance 5.7 Litre
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    Re: Severe spark knock under partial throttle

    With a carberator sucking seafoam into one of those hoses is the same thing as pouring it down the carb. If you hold open the throttle with the engine off and look down inside the carb it goes straight into the intake.

  3. #18
    TopherS is offline Cadillac Owners Fanatic
    Automobile(s): '08 DTS LuxIII (70K mi.), '06 SRX V6-AWD (40K mi.)
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    Re: Severe spark knock under partial throttle

    An update:

    * Since using the Marvel Mystery Oil, it seems that the car is a touch more smooth/responsive and acceleration a bit more brisk...but again, I could just be trying to wish this into existence.

    * I've been trying to notice if there's been any more smoke...but it's been raining for past 2 days, so it's hard to tell...but haven't seen any.

    * As you all pointed out, the treatment might have cleaned the top end, but the spark knock is still there. I even noticed it knocking right at startup the other day (warm engine).

    * I don't know if this has anything to do with it...but Monday was about 75*F and yesterday/today have been over 20*F colder...and I've noticed less knocking as it's been colder. And when the problem was really bad last year, it was when the weather was warm...even had issues with power loss with hot weather.

    * I'm not due for an oil change for another 2K miles, but it's been 2 months since the last oil change so it's nearly time...I'll switch to 5W30.

    * I've never in my life worked on a distributor, except to change the cap/rotor. NAPA has reman distributors for about $135 or so, but I don't know if it's worth changing or trying to work with the one I've got...but since I don't know what I'm doing, I have to rely on mechanics for help. Advice?

  4. #19
    jamespowers is offline Cadillac Owners Connoisseur
    Automobile(s): 1986 Brougham, 1975 Eldorado, 2008 Escalade
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    Re: Severe spark knock under partial throttle

    Quote Originally Posted by TopherS View Post
    An update:

    * Since using the Marvel Mystery Oil, it seems that the car is a touch more smooth/responsive and acceleration a bit more brisk...but again, I could just be trying to wish this into existence.

    * I've been trying to notice if there's been any more smoke...but it's been raining for past 2 days, so it's hard to tell...but haven't seen any.

    * As you all pointed out, the treatment might have cleaned the top end, but the spark knock is still there. I even noticed it knocking right at startup the other day (warm engine).

    * I don't know if this has anything to do with it...but Monday was about 75*F and yesterday/today have been over 20*F colder...and I've noticed less knocking as it's been colder. And when the problem was really bad last year, it was when the weather was warm...even had issues with power loss with hot weather.

    * I'm not due for an oil change for another 2K miles, but it's been 2 months since the last oil change so it's nearly time...I'll switch to 5W30.

    * I've never in my life worked on a distributor, except to change the cap/rotor. NAPA has reman distributors for about $135 or so, but I don't know if it's worth changing or trying to work with the one I've got...but since I don't know what I'm doing, I have to rely on mechanics for help. Advice?
    If you are going to change the oil soon then you might as well flush the oil system with some Seafoam as well. Put about 1/3rd of the can of Seafoam in the oil and run it for no more than about 100 miles. By then it will be so black that you will want to change it anyway.

    ----------

    Quote Originally Posted by brougham View Post
    With a carberator sucking seafoam into one of those hoses is the same thing as pouring it down the carb. If you hold open the throttle with the engine off and look down inside the carb it goes straight into the intake.
    I am sure you are right but my carb is already clean.

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